The present invention relates to a multicore fiber that is preferable to the case of multiplexing and demultiplexing light beams in different modes.
In optical communications using optical fibers, multimode communications are known, in which information is superposed on a light beam in the LP01 mode (the fundamental mode) as well as information is superposed on light beams in LP modes higher than the fundamental mode, such as the LP11 mode for information communications. In multimode communications, a plurality of LP mode light beams propagated through one core is demultiplexed to a plurality of optical fibers, or LP mode light beams different from each other, which are propagated through a plurality of optical fibers, are multiplexed on one optical fiber.
Patent Literature 1 below describes a multicore fiber that can demultiplex a plurality of LP mode light beams propagated through one core to a plurality of cores or can multiplex light beams propagated through a plurality of cores on one core as LP mode light beams different from each other. The multicore fiber of Patent Literature 1 below includes a core disposed in the center of a cladding and cores disposed around the core. This multicore fiber can demultiplex a plurality of LP mode light beams propagated through the center core to a plurality of other cores disposed around the center core or can multiplex a light beam propagated through the plurality of cores on the center core as LP mode light beams different from each other. In order to allow mode-multiplexing and mode-demultiplexing as described above, in the multicore fiber, the plurality of cores is disposed being matched with the field shapes of the mode light beams.
[Patent Literature 1] WO/2015/129775 A